The present invention relates to vacuum interrupters, and more particularly to configurations of the conductive leads which are connected to vacuum interrupters.
In FIG. 1, schematically illustrating prior art, there is shown a vacuum interrupter 10 with prior art conductive leads 11 and 12 providing a path for current that is subject to interruption by the vacuum interrupter 10. The vacuum interrupter 10 shown is a conventional vacuum interrupter comprising first and second, separable contacts 14 and 15. The first and second contacts 14 and 15 comprise spiral finger portions 14a-14d and 15a-15d, respectively. The purpose of the foregoing spiral finger portions is to generate a magnetic field in the space between the contacts 14 and 15 for implementing rotation of an arc (not shown) that is drawn between the contacts 14 and 15 upon separation thereof. Such rotation is about the axis of the contacts 14 and 15, in a generally circular path. The reason for having the arc thus rotated is to prevent the arc from unduly heating the contacts 14 and 15 by remaining at a solitary location on each of the contacts.
It has been discovered by the present inventors that the foregoing magnetic arc rotation feature of the vacuum interrupter 10 is adversely affected by a magnetic field generated by current flowing in the conductive leads 11 and 12. This is due to the configuration of these conductive leads, which includes a sharp bend between the conductive lead 11 and a contact stem 17, and a further sharp bend between the conductive lead 12 and a contact stem 18. This configuration results in a substantial magnetic field impinging or encroaching upon the space between the first and second contacts 14 and 15 (that is, the space where an arc is drawn), which magnetic field, in turn, results in a force that pushes such an arc to the rightmost portions of the contacts 14 and 15, as illustrated in FIG. 1. The present inventors have determined that such a force is capable of overcoming the force that would otherwise drive the arc around the contacts 14 and 15 in a generally circular path. As a result of this, the peak current interruption capability of the prior art vacuum interrupter 10 is substantially reduced.